If you are under age 59 1/2 and do not meet any of the exceptions to the penalty then the additional 10% tax will apply. If the tax was due to an IRS levy then the penalty would not apply.
The exceptions that are available are explained on pages 53 - 55 of IRS Publication 590 - http://www.irs.gov/pub/irs-pdf/p590.pdf
Enrolled Agent
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